Block Diagonalization Precoding Research Articles

Hybrid block diagonalization precoding for multi-user weighted sum-rate maximization

Hybrid block diagonalization precoding for multi-user weighted sum-rate maximization

Kinerja Multi-user MIMO OFDM dengan Block-Diagonalization Precoding

Multiple-input multiple-output (MIMO) is a transmission technology that uses more than one antenna both on the transmitter side and on the receiver side. In the communication services, the system will involve more than one active user who uses one base station (BS) together so that it is called multi-user MIMO (MU-MIMO). This paper discusses the performances of MU-MIMO when it uses block diagonalization (BD) precoding and applies minimum mean squared error (MMSE) detector. As a comparison we also apply zero-forcing (ZF) detector. From the simulations that have been done, it is found that the MMSE had better performances than the ZF detector in terms of BER. We also consider the performance when users are moving. The simulation results show that BER performances are decrease slowly when users are moving.

Efficient User Grouping for MU-MIMO Visible Light Communications Based on Block Diagonalization

This paper investigates efficient user grouping methods for multi-user multi-input multi-output (MU-MIMO) visible light communication (VLC) systems. Block diagonalization (BD) precoding is considered for interference avoidance. In addition, time division multiplexing (TDM) is applied to perform user grouping when the number of users exceeds the limit of BD precoding based on the number of light emitting diode (LED) transmitters and the total number of users' photodiodes (PDs). User grouping methods are proposed based on pairwise interference considerations among users in the same group. The proposed methods can be implemented through integer linear programming (ILP), which requires less computation than exhaustive search. The numerical results on the average minimum user throughputs over random scenarios indicate that the proposed hybrid method can significantly outperform random user grouping and performs reasonably well compared to exhaustive search. Finally, this study demonstrates that, when BD precoding greatly attenuates the desired user signals, user grouping can help improve minimum user throughputs even though BD precoding can support all users as a single group.

Multi-User Scheduling for 6G V2X Ultra-Massive MIMO System.

6G vehicle-to-everything (V2X) communication will be combined with vehicle automatic driving technology and play an important role in automatic driving. However, in 6G V2X systems, vehicle users have the characteristics of high-speed movement. Therefore, how to provide stable and reliable wireless link quality and improve channel gain has become a problem that must be solved. To solve this problem, a new multi-user scheduling algorithm based on block diagonalization (BD) precoding for 6G ultra-massive multiple-input multiple-output (MIMO) systems is proposed in this paper. The algorithm takes advantage of the sensitive nature of BD precoding to channel correlation, uses the Pearson coefficient after matrix vectorization to measure the channel correlation between users, defines the scheduling factor to measure the channel quality according to the user noise enhancement factor, and jointly considers the influence of the correlation between user channels and channel quality, ensuring the selection of high-quality channels while minimizing channel correlation. Simulation results show that compared with the multi-user scheduling algorithm based on subspace correlation, condition number, and geometric angle, the proposed algorithm can obtain higher user channel gain, effectively reduce the system bit error rate, and can be applied to 6G V2X communication.

Block Diagonalization Precoding and Power Allocation for Multiple-Antenna Systems With Coarsely Quantized Signals

In this work, we present block diagonalization and power allocation algorithms for large-scale multiple-antenna systems with coarsely quantized signals. In particular, we develop Coarse Quantization-Aware Block Diagonalization <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\scriptstyle \mathrm {\left ({CQA-BD}\right)}}$ </tex-math></inline-formula> and Coarse Quantization-Aware Regularized Block Diagonalization <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\scriptstyle \mathrm {\left ({CQA-RBD}\right)}}$ </tex-math></inline-formula> precoding algorithms that employ the Bussgang decomposition and can mitigate the effects of low-resolution signals and interference. Moreover, we also devise the Coarse Quantization-Aware Most Advantageous Allocation Strategy <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\scriptstyle \mathrm {\left ({CQA-MAAS}\right)}}$ </tex-math></inline-formula> power allocation algorithm to improve the sum rate of precoders that operate with low-resolution signals. An analysis of the sum-rate performance is carried out along with computational complexity and power consumption studies of the proposed and existing techniques. Simulation results illustrate the performance of the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\scriptstyle \mathrm {CQA-BD}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\scriptstyle \mathrm {CQA-RBD}}$ </tex-math></inline-formula> precoding algorithms, and the proposed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\scriptstyle \mathrm {CQA-MAAS}}$ </tex-math></inline-formula> power allocation strategy against existing approaches.

Energy-Efficient Multi-Antenna Hybrid Block Diagonalization Precoding and Combining for MmWave Massive Multi-User MIMO Systems

The millimeter-wave (mmWave) massive multi-user multiple-input multiple-output (MU-MIMO) can significantly improve the throughput and spectral efficiency by equipping multi-antenna at both the base station (BS) and the users, which is greatly promising technologies for wireless communication systems. However, the large hardware requirement and high energy consumption are great hindrances. To effectively reduce the hardware and computational complexity and achieve a better trade-off between system complexity and performance, we propose an energy-efficient split sub-connected architecture based multi-user hybrid block diagonalization (BD) precoding and combining (Sub MU-HBD) scheme. The proposed Sub MU-HBD scheme employs the split sub-connected architecture to reduce the hardware complexity and improve spectral efficiency. Additionally, to significantly reduce the inter-user interference and further lessen the computational complexity, a low-dimensional digital precoding and combining scheme based on the BD is proposed. Furthermore, we propose a proportional water-filling power allocation algorithm to ensure optimal power distribution to users and improve energy efficiency. The simulation results demonstrate that the proposed Sub MU-HBD scheme can achieve near-optimal, and at times even better performance than some existing schemes.

Low complexity transmitter precoding for MU MIMO-OTFS

Orthogonal time frequency space (OTFS) is a recently introduced modulation technique that multiplexes information symbols in the delay-Doppler (DD) domain rather than the time frequency (TF) domain as in traditional multi-carrier modulation such as orthogonal frequency division multiplexing (OFDM). It has been shown that OTFS outperforms OFDM in a high Doppler environment. OTFS can be utilized in the multi-user (MU) multi-input multi-output (MIMO) scenario, exactly as OFDM. In this paper, we focus on low complexity transmitter precoding for MU MIMO-OTFS. The computational complexity of traditional transmitter precoding is too high in the MU MIMO-OTFS system. We propose two low complexity precoding algorithms for MU MIMO-OTFS. The proposed low complexity precoding utilizes the specific property of the OTFS channel in the DD domain; meanwhile, the inversion of a large dimensional matrix is achieved by employing the matrix inversion lemma. The simulation results illustrate that our proposed precoding algorithms work well in the MU MIMO-OTFS system, MU MIMO-OTFS outperforms MU MIMO-OFDM and the performance of MU MIMO-OTFS is robust to different user speeds. Meanwhile, compared with block diagonalization (BD) precoding, our proposed precoding significantly reduces the computational complexity with a small performance loss.

Transceiver Design for Full-Duplex UAV Based Zero-Padded OFDM System With Physical Layer Security

In this paper, multi-antenna transceiver for zero-padded orthogonal frequency division multiplexing (OFDM) system is designed at mmWave by integrating full-duplex unmanned aerial vehicle (UAV) into the terrestrial cellular networks. Assuming that there exist no direct communication links between the ground base station (GBS) and the mobile users due to unexpected blockages from high storied buildings in urban area, the UAV applies decode-and-forward cooperative strategy on the received OFDM signals transmitted from GBS and re-transmits to the ground mobile users and passive eavesdropper. In this proposed system, intertwining logistic map (ILM)-cosine transform aided encryption algorithm combined with artificial noise enhancing physical layer security (PLS) is introduced. Also walsh-hadamard transform technique integrated with QR-decomposition based zero forcing (ZF) block diagonalization (QR-ZF-BD) precoding for multi-user interference reduction and non-iterative clipping and filtering technique for peak to average power ratio (PAPR) reduction are utilized. In addition, Low density parity check (LDPC) and repeat and accumulate (RA) channel coding with cholesky decomposition based ZF and minimum mean square error signal detection schemes for improved bit error rate (BER) are also introduced. Numerical results demonstrate the effectiveness of the proposed system in terms of PLS for color image transmission at high order digital modulation (16-PSK and 16-QAM). At the complementary cumulative distribution function of probability level 1-6%, the estimated PAPR is found to have value of 6 dB.The three users achieve BER <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$= 1\times {10}^{-4}$ </tex-math></inline-formula> at signal-to-noise ratio of 1.5 dB, 4 dB and 6 dB under RA channel coding and 16-QAM digital modulation.

Block diagonalization precoding and power allocation for clustering small-cell networks

The clustering network is a solution to improve data-rate transmission in small-cells. In this case, clustering small-cells (CSCs) adopt a multiple antennas concept. The multiple antennas are used to maximize the downlink data-rate transmission at the users, but it requires precoding techniques to minimize interference among CSC users. This paper proposes a block diagonalization (BD) as a precoding technique for minimizing interference among CSC users. The performance of the BD precoding implemented on the clustering network under various numbers of small-cells. The CSC also implements a water-filling power allocation (PA-CoopWF) to distribute the available transmission power along with the CSCs antennas. To show the performance, our paper simulates two types of precoding techniques; those are the proposed BD and minimum mean square error (MMSE) in CSCs. Based on the receiver user parts under the overlapping coordination of CSCs, our method based on the BD precoding achieves considerably higher data-rate transmission compared to the MMSE precoding, especially on larger clusters. The simulation also shows that by implementing CSC with the BD in short-range distances and higher numbers of antennas, it promotes better data-rate performances compared to the MMSE precoding by 2.75 times at distance 100m and 67% at 50 antennas.

Regularized Block Diagonalization Precoding Transmission Scheme Using Relay in NOMA

In Multiuser Multiple Input Multiple Output (MU-MIMO) system, Block Diagonalization (BD) and Regularized Block Diagonalization (RBD) are schemes which completely suppress Inter-User Interference (IUI). BD and RBD use the same number of RF chains and transmit antennas as the number of data streams in general. This paper proposes a RBD precoding transmission scheme using relay in Non-orthogonal Multiple Access (NOMA) system to reduce complexity of transmitter structure. The proposed scheme uses only half the number of RF chains and transmit antennas compared to the conventional RBD scheme. The number of Singular Value Decomposition (SVD) of the proposed scheme is also reduced compared to the conventional RBD, while Successive Interference Cancellation (SIC) is needed additionally. However, the proposed algorithm can achieve low computational complexity since SIC is simpler than SVD. However, the proposed scheme has poor BER performance compared to the conventional RBD. Therefore, further study is needed to increase the BER performance while the complexity is reduced.

Partial Nulling Regularized Block Diagonalization Using Unfair Channel Selection for Post-Coding with Low-Complexity

A number of requirements for 5G mobile communication are satisfied by adopting multi-user multiple input multiple output (MU-MIMO) systems. The inter user interference (IUI) which is an inevitable problem in MU-MIMO systems becomes controllable when the precoding scheme is used. The proposed scheme, which is one of the precoding schemes, is built on regularized block diagonalization (RBD) precoding and utilizes the partial nulling concept, which is to leave part of the IUI at the same time. Diversity gain is obtained by leaving IUI, which is made by choosing the row vectors of the channel matrix that are not nullified. Since the criterion for choosing the row vectors of the channel is the power of the channel, the number of selected row vectors of the channel for each device can be unfair. The proposed scheme achieves performance enhancement by obtaining diversity gain. Therefore, the bit error rate (BER) performance is better and the computational complexity is lower than RBD when the same data rate is achieved. When the number of reduced data streams is not enough for most devices to achieve diversity gain, the proposed scheme has better performance compared to generalized block diagonalization (GBD). The low complexity at the receiver is achieved compared to GBD by using the simple way to remove IUI.

Smart Switching Strategy-Based Supervision Rule to Mitigate the Problem of Pilot Contamination in Massive MIMO Systems

Despite the large benefits that can be fulfilled through the exploitation of Massive Multi-input Multioutput (M-MIMO), this technology still constrained by a well-known constraint, called as pilot contamination problem (PCP), which is the main consequence of, simultaneously, reusing the same set of orthogonal pilot sequences (OPSs) for the users of several cells. Due to the scarcity of the OPS resources, the reuse of the same set of the OPSs for the users of different cells is unavoidable. Hence, this work proposes a novel decontaminating strategy, which is aimed at guaranteeing a trade-off between the use of the OPSs and the mitigation of the PCP. Specifically, to make the use of the available OPSs better, we propose the consolidation of two powerful decontaminating strategies. Under a derived supervision rule (SR), these strategies are the soft pilot reuse-based multicell block diagonalization precoding (SPR-MBDP) and the weighted graph coloring-based pilot assignment (WGC-PA). The SR enables the switching mechanism between the two strategies, which leads to address the PCP with a fewer number of the OPSs compared to the SPR-MBDP, therefore boosting the per-cell achievable rate. Simulation results prove the effectiveness of our proposed strategy.

Multiuser Precoded MIMO Visible Light Communication Systems Enabling Spatial Dimming

In this article, a new indoor multiuser (MU) multiple-input–multiple-output (MIMO) visible light communication (VLC) system is proposed, where the dynamic range of the light emitting diodes (LED-DR) and illumination requirements are taken into consideration. Exploiting the characteristics of LED-DR and the block diagonalization precoding (BDP) technique, we design a weight-adjusted BDP (WA-BDP) scheme that can exploit the LED-DR to offer a high performance in terms of bit error rate (BER). Moreover, utilizing the LED array equipped with a number of LEDs, a spatial dimming (SD) mechanism based on LED selection is employed to fulfill the uniform illumination requirement for typical indoor scenarios. Finally, we combine the WA-BDP technique and SD to form the proposed spatially-dimmed, weight-adjusted block diagonalization precoded (SD-WA-BDP) MU-MIMO-VLC system, where the LED-DR is fully utilized to support simultaneous illumination and communication. In addition, two options of the SD-WA-BDP scheme are developed to manage the performance and complexity tradeoff. Simulation results demonstrate the superiority of the proposed scheme.

Linear Precoding and Stream Combining for Rate Splitting in Multiuser MIMO Systems

This letter develops practical linear precoding and stream combining techniques for rate-splitting (RS) in multiuser multiple-input multiple-output (MIMO) systems. We propose linear combining techniques based on the Min-Max, the maximum ratio and the minimum mean-square error criteria along with Regularized Block Diagonalization (RBD) precoders for RS-based multiuser multiple-antenna systems. An analysis of the sum rate performance is carried out, leading to closed-form expressions. Simulations show that the proposed combining schemes offer a significant sum rate performance gain over conventional linear precoding schemes.

SCLNR-Based Precoding Scheme for Multi-User MIMO SWIPT Systems

A new precoder design scheme, called the signal-controlled-leakage-noise ratio (SCLNR), is proposed. The proposed SCLNR precoder is designed to enhance the data rate and harvesting energy simultaneously. Specifically, the proposed SCLNR precoder is designed to increase the leakage signal toward energy users and decrease leakage signal toward data users, and can be attained in a closed-form solution. Numerical results are provided to evaluate the performance of the proposed SCLNR precoder for simultaneous wireless-information and power-transfer systems. The proposed SCLNR precoder achieve efficient performance compared with the precoder obtained from complicated iterative algorithm in terms of the computational complexity. The proposed SCLNR precoder outperforms a precoder that uses conventional signal-to-leakage-and-noise ratio based precoder and block diagonalization precoder for data users and energy beamformers for energy users in terms of the rate–energy region.

Enhancing Downlink Transmission in MIMO HetNet With Wireless Backhaul

We propose a transmission scheme that exploits the spatial degrees of freedom from large antenna arrays to maximize the downlink sum-rate of user equipment (UE) in a heterogeneous network. Our scheme incorporates the design of 1) a new precoder for the millimeter wave (mmWave) wireless backhaul; and 2) an enhanced small cell range expansion method for data link transmission. Aside from the advantage of lower implementation and computational complexity, the wireless backhaul precoder can simultaneously support multiple small access points with multi-streams. Under the constraint of wireless backhaul capacity, a downlink cooperation precoding algorithm is proposed to suppress the interference caused by small cell range expansion. Simulation results show that the proposed precoder in backhaul link can use a small number of radio frequency (RF) chains to achieve the sum-rate performance that approaches the one under traditional block diagonalization precoder, which requires the number of the RF chains to be comparable with that of antenna elements. Moreover, we give a lower bound for the overall UE sum-rate of the downlink cooperation precoding algorithm.

Large-Scale Analysis of Regularized Block Diagonalization Precoding for Physical Layer Security of Multi-User MIMO Wireless Networks

In this paper, we propose regularized block diagonalization (RBD) precoding using artificial noise (AN) for physical layer security in downlink multi-user MIMO wireless networks. We derive secrecy sum rate and asymptotic secrecy sum rate for the proposed scheme. The optimum power allocation for legitimate users and the AN signal are derived in closed form for optimal asymptotic secrecy sum rate. Our analysis shows that to achieve best performance, it is more efficient to degrade the performance of the eavesdropper than improving legitimate users' rates. We also study the impact of error in channel estimation on the system and derive closed-form SINR and secrecy sum-rate expressions for this case. Simulations show that the secrecy sum rate of RBD precoding outperforms the secrecy sum rate of regularized channel inversion by 0.5 bits/s/Hz. We also show that in the presence of channel estimation error, our approximate closed forms for secrecy sum rate are very closed to the actual secrecy sum rate over a wide range of SNR and channel estimation error values.

Dynamic Transmission Policy for Multi-Pair Cooperative Device-to-Device Communication With Block-Diagonalization Precoding

This paper proposes a dynamic precoding and power allocation policy for mutually cooperative device-to-device (D2D) transmitter–receiver pairs that underlay a cellular system in the uplink. The cooperative transmission consists of two phases: a data-sharing phase (i.e., phase 1) and a joint transmission phase (i.e., phase 2). Multicast precoders are used in phase 1 and coordinated block-diagonalization precoders are considered in phase 2. The precoders are jointly designed to maximize the long-term utility of the D2D users subject to long-term individual power and rate-gain constraints and an instantaneous interference constraint at the base-station. The long-term objective and constraints allow cooperating users to adapt their resources more flexibly over time, but increase the complexity of the design. By adopting the Lyapunov optimization framework and by constructing virtual queues to record the temporal evolution of the system states, the long-term utility maximization problem can be decoupled into a series of short-term weighted-rate-minus-energy-penalty (WRMEP) optimization problems that can be solved efficiently. A low-complexity algorithm is further proposed for solving the WRMEP problem when multicasting in the data-sharing phase is performed by a spatially white input. Theoretical performance guarantees and a bound on the virtual queue backlogs are also derived.

Resource allocation and interference suppression with PCA for multicell MU-MIMO systems

This paper studies a resource allocation scheme and precoding design to increase the number of quality of service (QoS)-satisfied user equipments (UEs) for multicell multiuser multiple-input-multiple-output downlink systems. The main challenge in such multicell systems is the co-channel interference, including intra-user interference (IUI) and inter-cell interference (ICI). To deal with both IUI and ICI, most conventional schemes aim to maximize the signal to interference plus noise ratio or throughputs through enormous channel state information (CSI) exchange among base stations. In order to avoid such tremendous overhead, this work proposes a novel framework, containing a distributed subcarrier assignment and a block diagonalization (BD) precoding, to cope with both types of interferences based on limited exchanged information of subcarrier-assignment and local CSIs (channel gains). In the subcarrier-assignment process, each sector’s base station independently assigns a subset of the served UEs to be served over the subcarrier. The channel gains of a particular subcarrier hold a semi-orthogonal property for that subset. Then, on the basis of limited exchanges of information, a BD-type precoding is presented to completely eliminate all IUI and suppress the major part of the leakage interference to the adjacent sectors by exploiting principal component analysis. The simulation results indicate that the proposed framework can provide more QoS-satisfied UEs than that obtained in a previous work.

Distributed Transmission Scheduling and Power Allocation in CoMP

The performance of wireless networks can be largely enhanced by coordinated multipoint (CoMP). To design an efficient CoMP in multiuser multiple-input multiple-output scenario, conventional transmission scheduling and power allocation are usually performed in a static and centralized manner. In this paper, we focus on dynamic and distributed transmission scheduling and power allocation. We first determine the coordinated base-station sets (defined as CBSs) candidates in each subband by the channel energy ( i.e., square Frobenius norm of channel matrix) of each user. Each CBS candidate contains a set of coordination base-stations and edge users. By chordal distance, we can measure the orthogonality between space spanned of users in the same CBS candidate. Then, we propose two heuristic user scheduling algorithms based on channel energy and chordal distance between users to determine the set of users served by each CBS candidate. The first algorithm is based on an open problem, which reveals the philosophy of user scheduling with orthogonalization threshold guarantee. The second one deals with user scheduling by selecting a set of edge users with the largest total channel energy and orthogonalization threshold guarantee. With the total channel energy per CBS candidate, the CBSs and their served edge users can be determined. Then, water-filling power allocation is further applied to CBSs with block diagonalization precoding. Algorithm performance is demonstrated by extensive simulations.